Initiator composition for curing resin

ABSTRACT

An initiator composition, including at least two compounds represented by the chemical formula R—CO—O—O—CO—R and a compound represented by R 1 —O—O—R 2 , where R represents a C 2 -C 12  alkyl or a C 6 -C 10  aryl or substituted aryl, and R 1  and R 2  independently, at each occurrence, represent a C 1 -C 10  alkyl or a C 6 -C 10  aryl.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of International Patent Application No. PCT/CN2013/074225 with an international filing date of Apr. 16, 2013, designating the United States, now pending, and further claims priority benefits to Chinese Patent Application No. 201210116111. X filed Apr. 19, 2012. The contents of all of the aforementioned applications, including any intervening amendments thereto, are incorporated herein by reference. Inquiries from the public to applicants or assignees concerning this document or the related applications should be directed to: Matthias Scholl P.C., Attn.: Dr. Matthias Scholl Esq., 245 First Street, 18th Floor, Cambridge, Mass. 02142.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to an initiator composition.

2. Description of the Related Art

A typical curing system for unsaturated polyester resins at room temperature employs a ketone peroxide such as methyl ethyl ketone peroxide or cyclohexanone peroxide as an initiator, a cobalt salt as an accelerator, or employs benzoyl peroxide as an initiator, tertiary amine as an accelerator. However, the curing system can only cure unsaturated polyester resins at room temperature, if the temperature is no more than 15° C., the gel time is very long, the curing speed and the degree of cure are very low, and the mechanical properties of the cured substances leave much to be desired.

SUMMARY OF THE INVENTION

In view of the above-described problems, it is one objective of the invention to provide an initiator composition that can accelerate the curing speed of unsaturated polyester resins at different temperature particularly at temperatures no more than 15° C., and improve the mechanical properties of the cured substances.

The curing of unsaturated polyester resins includes three stages: gelation, shaping, and aging. The gelation means the resins transform from a viscous flow state to a semisolid gel. The shaping means the resins transform from the semisolid gel to have a certain hardness and fixed shape. The aging means the shaped resins are being hardened naturally to have stable chemical and physical properties. The aging generally last for 3-10 days.

The principle of the curing of unsaturated polyester resins is summarized as follows. An initiator can initiate the chain initiation of unsaturated polyester resins. The initiator is a compound comprising a weak bond and tends to decompose into free radicals. In the presence of thermal or radiant energy, the weak bond breaks and the initiator decomposes to yield two free radicals. The resulting free radicals attack the unsaturated polyester resins to produce radical monomers thereby accelerating the curing of the resins.

To achieve the above objective, in accordance with one embodiment of the invention, there is provided an initiator composition comprising: at least two compounds represented by a formula of R—CO—O—O—CO—R and a compound represented by R₁—O—O—R₂, where R represents a C₂-C₁₂ alkyl or a C₆-C₁₀ aryl or substituted aryl, R₁ and R₂ independently, at each occurrence, represents a C₁-C₁₀ alkyl or a C₆-C₁₀ aryl.

In a class of this embodiment, the two compounds represented by the formula of R—CO—O—O—CO—R are a diacyl peroxide selected from the group consisting of benzoyl peroxide, 2,4-dichlorobenzene acyl peroxide, lauroyl peroxide, and diacetyl peroxide, and the compound represented by R₁—O—O—R₂ is an alkyl peroxide selected from the group consisting of dicumyl peroxide, di-t-butyl peroxide, and t-butyl cumyl peroxide.

In a class of this embodiment, the initiator composition comprises between 50 and 95 parts by weight of the two compounds represented by the formula of R—CO—O—O—CO—R and between 5 and 50 parts by weight of the compound represented by R₁—O—O—R₂.

In a class of this embodiment, the initiator composition comprises between 75 and 95 parts by weight of the two compounds represented by the formula of R—CO—O—O—CO—R and between 5 and 25 parts by weight of the compound represented by R₁—O—O—R₂.

In a class of this embodiment, the initiator composition comprises 75 parts by weight of the diacyl peroxide and 25 parts by weight of the alkyl peroxide. Specifically, the diacyl peroxide comprises 25 parts by weight of the benzoyl peroxide, 30 parts by weight of 2,4-dichlorobenzene acyl peroxide, and 20 parts by weight of lauroyl peroxide, and the alkyl peroxide is di-t-butyl peroxide.

In a class of this embodiment, the initiator composition comprises 95 parts by weight of the diacyl peroxide and 5 parts by weight of the alkyl peroxide. Specifically, the diacyl peroxide comprises 35 parts by weight of the benzoyl peroxide, 40 parts by weight of 2,4-dichlorobenzene acyl peroxide, 10 parts by weight of lauroyl peroxide, and 10 parts by weight of diacetyl peroxide, and the alkyl peroxide is t-butyl cumyl peroxide.

In a class of this embodiment, the initiator composition comprises 90 parts by weight of the diacyl peroxide and 10 parts by weight of the alkyl peroxide. Specifically, the diacyl peroxide comprises 40 parts by weight of the benzoyl peroxide and 50 parts by weight of 2,4-dichlorobenzene acyl peroxide, and the alkyl peroxide is dicumyl peroxide.

In a class of this embodiment, the initiator composition further comprises a compound represented by a formula of R₁—CO—O—O—R₂, where R₁ represents a C₁-C₁₀ alkyl or a C₆-C₁₀ aryl, R₂ represents a C₁-C₁₀ alkyl, the compound represented by the formula of R₁—CO—O—O—R₂ is a carboxylic ester peroxide selected from the group consisting of tert-butyl peroxybenzoate (TBPB), tert-Butyl peroxy diethyl acetate, t-butyl peroctoate (TBPO), and the initiator composition comprises between 70 and 85 parts by weight of the two compounds represented by the formula of R—CO—O—O—CO—R, between 5 and 15 parts by weight of the compound represented by R₁—O—O—R₂, and between 5 and 15 parts by weight of the compound represented by a formula of R₁—CO—O—O—R₂.

In a class of this embodiment, the diacyl peroxide is 75 parts by weight, the alkyl peroxide is 12 parts by weight, and the carboxylic ester peroxide is 13 parts by weight, the diacyl peroxide comprises 35 parts by weight of benzoyl peroxide and 40 parts by weight of 2,4-dichlorobenzene acyl peroxide, the alkyl peroxide is dicumyl peroxide, and the carboxylic ester peroxide is tert-butyl peroxybenzoate.

Advantages according to embodiments of the invention are summarized as follows: the initiator composition can accelerate the curing speed of unsaturated polyester resins at different temperature particularly at temperatures no more than 15° C., and improve the mechanical properties of the cured substances.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is described hereinbelow with reference to accompanying drawings, in which:

FIG. 1 is a curve chart of a gel time of unsaturated polyester resins initiated by an initiator composition of the invention at different temperatures;

FIG. 2 is a local enlarged view of FIG. 1;

FIG. 3 is a curve chart of a curing time of unsaturated polyester resins initiated by an initiator composition of the invention at different temperatures; and

FIG. 4 is a local enlarged view of FIG. 3.

DETAILED DESCRIPTION OF THE EMBODIMENTS

For further illustrating the invention, experiments detailing an initiator composition are described below. It should be noted that the following examples are intended to describe and not to limit the invention.

Experiments show that diacyl peroxides comprising benzoyl peroxide, 2,4-dichlorobenzene acyl peroxide, lauroyl peroxide, and diacetyl peroxide have a short half time and low critical temperature, which can shorten the gel time of unsaturated polyester resins.

The alkyl peroxides comprising dicumyl peroxide, di-t-butyl peroxide, t-butyl cumyl peroxide have a high critical temperature, which can shorten the shaping time (also called the post curing time) of unsaturated polyester resins.

The carboxylic ester peroxides comprising tert-butyl peroxybenzoate (TBPB), tert-Butyl peroxy diethyl acetate, t-butyl peroctoate (TBPO) have a high critical temperature, which can shorten the curing time (which is a total of the gel time and the post curing time) of unsaturated polyester resins.

The unsaturated polyester resins involved in this invention are formed by the polycondensation of unsaturated dicarboxylic acids (anhydrides), saturated dicarboxylic acids (anhydrides), and diols or polyols. After the polycondensation, a diluent such as styrene, an inhibitor, and an accelerator are added to the resins, thereby producing a liquid pre-accelerated unsaturated polyester resin (the product can be purchased from the market).

The pre-accelerated unsaturated polyester resin is selected from the group consisting of phthalandione type unsaturated polyester resin, isophthalic unsaturated polyester resin, bisphenol A-type unsaturated polyester resin, dicyclopentadiene unsaturated polyester resin, hexachloro-endo-methylenetetrahydrophthalic acid-based unsaturated polyester acetate resin, vinyl ester resin, and allyl resin.

The pre-accelerated unsaturated polyester resin is mainly applied to but is not limited to artificial marble, artificial agate, putty, cement, bonding agent, and concrete, with a number-average molecular weight of 1000-10000, preferably, 1000-6000, and more preferably, 1000-3000.

The inhibitor is selected from the group consisting of hydroquinone, 2,5-di-tert-butyl hydroquinone, methyl hydroquinone, p-benzoquinone, 4-tert-butylcatechol, the accelerator is selected from the group consisting of N, N-dimethyl aniline, N, N-diethylaniline, N, N-dimethyl-p-toluidine, N-methyl —N-hydroxyethyl aniline, N-methyl-N-hydroxyethyl p-toluidine, N- methyl —N-hydroxypropyl p-toluidine, N, N-dihydroxyethyl aniline, and a homologue thereof.

The curing process of the invention is summarized as follows. 0.3-3.0 parts by weight of the initiator composition of the invention are added to 100 parts by weight of the pre-accelerated unsaturated polyester resin and mixed. In contrast to conventional initiators, the initiator composition can accelerate the curing speed of unsaturated polyester resins at different temperature particularly at temperatures no more than 15° C., and improve the mechanical properties of the cured substances.

The initiator composition comprises at least two compounds represented by a formula of R—CO—O—O—CO—R and a compound represented by R₁—O—O—R₂, where R represents a C₂-C₁₂ alkyl or a C₆-C₁₀ aryl or substituted aryl, R₁ and R₂ independently, at each occurrence, represents a C₁-C₁₀ alkyl or a C₆-C₁₀ aryl.

The two compounds represented by the formula of R—CO—O—O—CO—R are a diacyl peroxide selected from the group consisting of benzoyl peroxide, 2,4-dichlorobenzene acyl peroxide, lauroyl peroxide, and diacetyl peroxide, and the compound represented by R₁—O—O—R₂ is an alkyl peroxide selected from the group consisting of dicumyl peroxide, di-t-butyl peroxide, and t-butyl cumyl peroxide.

The initiator composition comprises between 50 and 95 parts by weight of the two compounds represented by the formula of R—CO—O—O—CO—R and between 5 and 50 parts by weight of the compound represented by R₁—CO—O—O—R₂.

The initiator composition comprises between 75 and 95 parts by weight of the two compounds represented by the formula of R—CO—O—O—CO—R and between 5 and 25 parts by weight of the compound represented by R₁—CO—O—O—R₂.

Specifically, the initiator composition comprises 75 parts by weight of the diacyl peroxide and 25 parts by weight of the alkyl peroxide. Specifically, the diacyl peroxide comprises 25 parts by weight of the benzoyl peroxide, 30 parts by weight of 2,4-dichlorobenzene acyl peroxide, and 20 parts by weight of lauroyl peroxide, and the alkyl peroxide is di-t-butyl peroxide.

The initiator composition comprises 95 parts by weight of the diacyl peroxide and 5 parts by weight of the alkyl peroxide. Specifically, the diacyl peroxide comprises 35 parts by weight of the benzoyl peroxide, 40 parts by weight of 2,4-dichlorobenzene acyl peroxide, 10 parts by weight of lauroyl peroxide, and 10 parts by weight of diacetyl peroxide, and the alkyl peroxide is t-butyl cumyl peroxide.

The initiator composition comprises 90 parts by weight of the diacyl peroxide and 10 parts by weight of the alkyl peroxide. Specifically, the diacyl peroxide comprises 40 parts by weight of the benzoyl peroxide and 50 parts by weight of 2,4-dichlorobenzene acyl peroxide, and the alkyl peroxide is dicumyl peroxide.

The initiator composition further comprises a compound represented by a formula of R₁—CO—O—O—R₂, where R₁ represents a C₁-C₁₀ alkyl or a C₆-C₁₀ aryl, R₂ represents a C₁-C₁₀ alkyl.

The compound represented by the formula of R₁—CO—O—O—R₂ is a carboxylic ester peroxide selected from the group consisting of tert-butyl peroxybenzoate (TBPB), tert-Butyl peroxy diethyl acetate, t-butyl peroctoate (TBPO).

The initiator composition comprises between 70 and 85 parts by weight of the two compounds represented by the formula of R—CO—O—O—CO—R, between 5 and 15 parts by weight of the compound represented by R₁—O—O—R₂, and between 5 and 15 parts by weight of the compound represented by a formula of R₁—CO—O—O—R₂.

The diacyl peroxide is 75 parts by weight, the alkyl peroxide is 12 parts by weight, and the carboxylic ester peroxide is 13 parts by weight, the diacyl peroxide comprises 35 parts by weight of benzoyl peroxide and 40 parts by weight of 2,4-dichlorobenzene acyl peroxide, the alkyl peroxide is dicumyl peroxide, and the carboxylic ester peroxide is tert-butyl peroxybenzoate.

The initiator composition is used for the curing of unsaturated polyester resins. The unsaturated polyester resins are selected from the group consisting of phthalandione type unsaturated polyester resin, isophthalic unsaturated polyester resin, bisphenol A-type unsaturated polyester resin, dicyclopentadiene unsaturated polyester resin, hexachloro-endo-methylenetetrahydrophthalic acid-based unsaturated polyester acetate resin, vinyl ester resin, and allyl resin.

The following are some examples for the initiator composition of the invention.

Initiator composition No. 1 (by weight), total weight is 100 parts:

-   -   benzoyl peroxide: 40 parts by weight;     -   2,4-dichlorobenzene acyl peroxide: 50 parts by weight;     -   dicumyl peroxide: 10 parts by weight.

Initiator composition No. 2 (by weight), total weight is 100 parts:

-   -   benzoyl peroxide: 35 parts by weight;     -   2,4-dichlorobenzene acyl peroxide: 40 parts by weight;     -   lauroyl peroxide: 10 parts by weight;     -   diacetyl peroxide : 10 parts by weight;     -   t-butyl cumyl peroxide: 5 parts by weight.

Initiator composition No. 3 (by weight), total weight is 100 parts:

-   -   benzoyl peroxide: 25 parts by weight;     -   2,4-dichlorobenzene acyl peroxide: 30 parts by weight;     -   lauroyl peroxide: 20 parts by weight;     -   di-t-butyl peroxide: 25 parts by weight.

Initiator composition No. 4 (by weight), total weight is 100 parts:

-   -   benzoyl peroxide: 25 parts by weight;     -   lauroyl peroxide: 25 parts by weight;     -   t-butyl cumyl peroxide: 50 parts by weight.

Initiator composition No. 5 (by weight), total weight is 100 parts:

-   -   benzoyl peroxide: 35 parts by weight;     -   2,4-dichlorobenzene acyl peroxide: 40 parts by weight;     -   tert-butyl peroxybenzoate: 13 parts by weight;     -   dicumyl peroxide: 12 parts by weight.

Initiator composition No. 6 (by weight), total weight is 100 parts:

-   -   benzoyl peroxide: 30 parts by weight;     -   diacetyl peroxide : 30 parts by weight;     -   lauroyl peroxide: 20 parts by weight;     -   tert-butyl peroxybenzoate: 5 parts by weight;     -   tert-butyl peroxy diethyl acetate: 10 parts by weight;     -   di-t-butyl peroxide: 5 parts by weight.

Initiator composition No. 7 (by weight), total weight is 100 parts:

-   -   benzoyl peroxide: 35 parts by weight;     -   lauroyl peroxide: 40 parts by weight;     -   tert-butyl peroxybenzoate: 10 parts by weight;     -   di-t-butyl peroxide: 6 parts by weight;     -   dicumyl peroxide: 9 parts by weight.

Initiator composition No. 8 (by weight), total weight is 100 parts:

-   -   benzoyl peroxide: 25 parts by weight;     -   diacetyl peroxide: 20 parts by weight;     -   lauroyl peroxide: 30 parts by weight;     -   2,4-dichlorobenzene acyl peroxide: 10 parts by weight;     -   tert-butyl peroxybenzoate: 5 parts by weight;     -   di-t-butyl peroxide: 10 parts by weight.

Initiator composition No. 9 (by weight), total weight is 100 parts:

-   -   benzoyl peroxide: 30 parts by weight;     -   2,4-dichlorobenzene acyl peroxide: 40 parts by weight;     -   tert-butyl peroxybenzoate: 5 parts by weight;     -   tert-butyl peroxy diethyl acetate: 10 parts by weight;     -   t-butyl peroctoate 10 parts by weight;     -   di-t-butyl peroxide: 5 parts by weight.

Initiator composition No. 10 (by weight), total weight is 100 parts:

-   -   benzoyl peroxide: 40 parts by weight;     -   diacetyl peroxide: 35 parts by weight;     -   tert-butyl peroxybenzoate: 10 parts by weight;     -   di-t-butyl peroxide: 5 parts by weight;     -   dicumyl peroxide: 5 parts by weight;     -   t-butyl cumyl peroxide 5 parts by weight.

EXAMPLE 1

At 0° C., 5° C., 10° C., 15° C., and 20° C., 100 g of dicyclopentadiene unsaturated polyester resin No. 946 from Jiangsu Yabang Coating Co., Ltd., 0.032 g of p-benzoquinone (technical grade), and 0.52 g of N, N-dimethyl p-toluidine (technical grade) were uniformly mixed. Thereafter, 1.5 g of the initiator composition No. 1 was added to the mixture, and the gel time and the curing time of the mixture were measured according to Chinese National Standard GB/T 7193-2008. The results are listed in Table 1.

The cured resin having a temperature of 5° C. was allowed to stand at 5° C. for 96 hours (this is an aging stage). Thereafter, the Barcol hardness of the cured resin was measured using a Barcol hardmeter (Beijing ShidaishanfengTechnology Co., HBA-1) according to Chinese National Standard GB/T 3854-2005, the bending strength of the cured resin was measured using a computer-controlled electronic universal testing machine (Shenzhen Reger Instrument Co.,Ltd, RGM-100) according to Chinese National Standard GB/T 2570-1995, and the impact strength of the cured resin was measured using an electronic combination-type impact testing machine (Chengde Jingmi Precision Testing Machine Co., Ltd., XJC-25D) according to Chinese National Standard GB/T 2571-1995. The results are listed in Table 2.

EXAMPLE 2

The experimental conditions and operations are the same as that in Example 1 except that the initiator composition No. 2 is substituted for the initiator composition No. 1. The gel time and curing time at different temperatures are listed in Table 1, and the Barcol hardness, the bending strength, and the impact strength of the cured resin at 5° C. are listed in Table 2.

EXAMPLE 3

The experimental conditions and operations are the same as that in Example 1 except that the initiator composition No. 3 is substituted for the initiator composition No. 1. The gel time and curing time at different temperatures are listed in Table 1, and the Barcol hardness, the bending strength, and the impact strength of the cured resin at 5° C. are listed in Table 2.

EXAMPLE 4

The experimental conditions and operations are the same as that in Example 1 except that the initiator composition No. 4 is substituted for the initiator composition No. 1. The gel time and curing time at different temperatures are listed in Table 1, and the Barcol hardness, the bending strength, and the impact strength of the cured resin at 5° C. are listed in Table 2.

EXAMPLE 5

The experimental conditions and operations are the same as that in Example 1 except that the initiator composition No. 5 is substituted for the initiator composition No. 1. The gel time and curing time at different temperatures are listed in Table 1, and the Barcol hardness, the bending strength, and the impact strength of the cured resin at 5° C. are listed in Table 2.

EXAMPLE 6

The experimental conditions and operations are the same as that in Example 1 except that the initiator composition No. 6 is substituted for the initiator composition No. 1. The gel time and curing time at different temperatures are listed in Table 1, and the Barcol hardness, the bending strength, and the impact strength of the cured resin at 5° C. are listed in Table 2.

EXAMPLE 7

The experimental conditions and operations are the same as that in Example 1 except that the initiator composition No. 7 is substituted for the initiator composition No. 1. The gel time and curing time at different temperatures are listed in Table 1, and the Barcol hardness, the bending strength, and the impact strength of the cured resin at 5° C. are listed in Table 2.

EXAMPLE 8

The experimental conditions and operations are the same as that in Example 1 except that the initiator composition No. 8 is substituted for the initiator composition No. 1. The gel time and curing time at different temperatures are listed in Table 1, and the Barcol hardness, the bending strength, and the impact strength of the cured resin at 5° C. are listed in Table 2.

EXAMPLE 9

The experimental conditions and operations are the same as that in Example 1 except that the initiator composition No. 9 is substituted for the initiator composition No. 1. The gel time and curing time at different temperatures are listed in Table 1, and the Barcol hardness, the bending strength, and the impact strength of the cured resin at 5° C. are listed in Table 2.

EXAMPLE 10

The experimental conditions and operations are the same as that in Example 1 except that the initiator composition No. 10 is substituted for the initiator composition No. 1. The gel time and curing time at different temperatures are listed in Table 1, and the Barcol hardness, the bending strength, and the impact strength of the cured resin at 5° C. are listed in Table 2.

COMPARATIVE EXAMPLE 1

The experimental conditions and operations are the same as that in Example 1 except that benzoperoxide (technical grade) is substituted for the initiator composition No. 1. The gel time and curing time at different temperatures are listed in Table 1, and the Barcol hardness, the bending strength, and the impact strength of the cured resin at 5° C. are listed in Table 2.

TABLE 1 Gel time and curing time at different temperatures Exam- Exam- Exam- Exam- Example Comparative Temperature Items ple 1 ple 2 ple 3 ple 4 Example 5 Example 6 Example 7 Example 8 Example 9 10 example 1 0° C. Gel time  4′  4′  4′  5′  5′  6′  7′  7′  9′  8′ 30′ 10″ 38″ 56″ 50″ 40″ 26″ 52″ 12″ 17″ 24″ 40″ Curing 20′ 21′ 22′ 22′ 10′ 11′ 12′ 12′ 13′ 13′ Not cured time 18″ 44″ 19″ 57″ 45″ 32″ 33″ 13″ 20″ 00″ 5° C. Gel time  2′  2′  3′  4′  3′  4′  5′  5′  7′  6′ 15′ 26″ 55″ 14″ 00″ 51″ 41″ 50″ 22″ 01″ 19″ 42″ Curing 14′ 16′ 16′ 17′  7′  8′  9′  8′ 10′ 10′ 38′ time 51″ 23″ 42″ 47″ 25″ 13″ 33″ 54″ 42″ 21″ 10″ 10° C. Gel time  1′  2′  2′  2′  2′  3′  4′  3′  5′  4′ 10′ 39″ 03″ 16″ 37″ 30″ 10″ 25″ 54″ 16″ 56″ 38″ Curing 10′ 12′ 12′ 13′  5′  5′  7′  6′  8′  7′ 23′ time 59″ 21″ 41″ 21 00″ 50″ 08″ 26″ 20″ 55″ 30″ 15° C. Gel time  1′  1′  1′  1′  1′  2′  3′  2′  4′  3′  6′ 01″ 24″ 37″ 54″ 49″ 21″ 21″ 52″ 07″ 44″ 20″ Curing  7′  8′  9′  9′  3′  4′  5′  4′  6′  5′ 12′ time 55″ 43″ 05″ 51″ 19″ 02″ 11″ 33″ 13″ 53″ 33″ 20° C. Gel time 51″ 55″  1′  1′  1′  1′  2′  2′  3′  3′  4′ 10″ 25″ 21″ 56″ 43″ 25″ 22″ 03″ 25″ Curing  5′  6′  6′  6′  2′  2′  3′  3′  4′  4′  7′ time 40″ 03″ 20″ 38″ 31″ 59″ 55″ 20″ 30″ 18″ 47″

TABLE 2 Barcol hardness, bending strength, and impact strength of cured resin at 5° C. Example Comparative Items Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Example 7 Example 8 Example 9 10 example 1 Barcol 49 47 48 45 49 47 45 48 46 47 32 hardness Bending 126 122 125 118 125 120 123 122 116 118 97 strength (MPa) Impact strength 2.8 2.9 2.8 2.5 2.7 2.6 2.7 2.6 2.8 2.8 1.8 (kJ/m²)

The gel time is calculated from the stirring to the occurrence of gel. The curing time is calculated from the stirring to the formation of a cured resin having certain hardness, which is total of the gel time and the shaping time.

Data in Table 1 correspond to FIGS. 1-4.

As shown in FIGS. 1-2, the initiator compositions in Examples 1-10 can significantly shorten the gel time of unsaturated polyester resins at low and normal temperatures.

As shown in FIGS. 3-4, the initiator compositions in Examples 1-10 can significantly shorten the curing time of unsaturated polyester resins at low and normal temperatures.

As shown in FIGS. 1 and 3, in Examples 1-4 and the comparative example 1, the gel time is significantly shortened, but the curing time is long, which does not benefit the construction; in Examples 5-10 and the comparative example 1, both the gel time and the curing time are significantly shortened, which is beneficial to the construction.

Data in Table 2 show that the initiator composition can significantly improve the degree of cure of unsaturated polyester resins at low temperatures, and improve the mechanical properties of cured resins.

While particular embodiments of the invention have been shown and described, it will be obvious to those skilled in the art that changes and modifications may be made without departing from the invention in its broader aspects, and therefore, the aim in the appended claims is to cover all such changes and modifications as fall within the true spirit and scope of the invention. 

The invention claimed is:
 1. An initiator composition, comprising 75 parts by weight of at least two first peroxides and 25 parts by weight of a second peroxide, wherein the at least two first peroxides comprise 25 parts by weight of benzoyl peroxide, 30 parts by weight of 2,4-dichlorobenzene acyl peroxide, and 20 parts by weight of lauroyl peroxide, and the second peroxide is di-t-butyl peroxide.
 2. An initiator composition, comprising 95 parts by weight of at least two first peroxides and 5 parts by weight of a second peroxide, wherein the at least two first peroxides comprise 35 parts by weight of benzoyl peroxide, 40 parts by weight of 2,4-dichlorobenzene acyl peroxide, 10 parts by weight of lauroyl peroxide, and 10 parts by weight of diacetyl peroxide, and the second peroxide is t-butyl cumyl peroxide.
 3. An initiator composition, comprising 90 parts by weight of at least two first peroxides and 10 parts by weight of a second peroxide, wherein the at least two first peroxides comprise 40 parts by weight of benzoyl peroxide and 50 parts by weight of 2,4-dichlorobenzene acyl peroxide, and the second peroxide is dicumyl peroxide.
 4. An initiator composition for expediting curing of an unsaturated polyester resin at room temperature, the initiator composition comprising: at least two first peroxides selected from the group consisting of benzoyl peroxide, 2,4-dichlorobenzene acyl peroxide, lauroyl peroxide, and diacetyl peroxide; a second peroxide selected from the group consisting of dicumyl peroxide, di-t-butyl peroxide, and t-butyl cumyl peroxide; and a carboxylic ester peroxide selected from the group consisting of tert-butyl peroxybenzoate (TBPB), tert-butyl peroxy diethyl acetate, t-butyl peroctoate (TBPO); wherein: the initiator composition comprises between 70 and 85 parts by weight of the at least two first peroxides, between 5 and 15 parts by weight of the second peroxide, and between 5 and 15 parts by weight of the carboxylic ester peroxide.
 5. The initiator composition of claim 4, wherein the initiator composition expedites the curing of an unsaturated polyester resin at a temperature not higher than 15° C.
 6. An initiator composition, comprising at least two first peroxides, a second peroxide, and a carboxylic ester peroxide; wherein the at least two first peroxides are 75 parts by weight; the second peroxide is 12 parts by weight; the carboxylic ester peroxide is 13 parts by weight; the at least two first peroxides comprise 35 parts by weight of benzoyl peroxide and 40 parts by weight of 2,4-dichlorobenzene acyl peroxide; the second peroxide is dicumyl peroxide; and the carboxylic ester peroxide is tert-butyl peroxybenzoate. 